Amazon.com is suing the Pentagon for excluding a $ 10 billion bid to provide so-called "cloud computing" services to the ministry, a bid awarded to Microsoft.
Amazon has filed a legal complaint with the Federal Claims Court, seeking to challenge the Pentagon's decision.
Details of the complaint were not disclosed, but Amazon said earlier this month that "there are shortcomings, errors and clear bias" in the way the bids are evaluated.
"We believe it is important for our state that the government and its elected ministers manage the procurement objectively and in a manner free of political influence," a company spokesman said.
Amazon was considered the most likely to win the contract, but repeated criticism by President Donald Trump of the company President Jeff Bezos cast doubt on the process, according to the same source.
The Associated Press quoted Defense Minister Mark Esper that the purchase was made to some extent without external influence.
Earlier this month, Amazon was surprised to lose the contract on cloud data storage technology, which Microsoft won late last month.
Amazon considers itself in a statement as clearly leading in computational computing. "We are surprised," she said.
Under the 10-year contract, Microsoft will provide important and urgent requirements for the defense infrastructure project, known as Gidai, according to the Pentagon.